[PATCH] libata: EH / pio tasks synchronization

This patch makes sure that pio tasks are flushed before proceeding
with EH.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>

2 files changed, 55 insertions, 4 deletions

diff --git a/drivers/scsi/libata-core.c b/drivers/scsi/libata-core.c
index 249e67fab81f..9a785cf0c5b1 100644
--- a/drivers/scsi/libata-core.c
+++ b/drivers/scsi/libata-core.c
@@ -1074,19 +1074,66 @@ static unsigned int ata_pio_modes(const struct ata_device *adev)
 static inline void
 ata_queue_packet_task(struct ata_port *ap)
 {
-        queue_work(ata_wq, &ap->packet_task);
+        if (!(ap->flags & ATA_FLAG_FLUSH_PIO_TASK))
+                queue_work(ata_wq, &ap->packet_task);
 }
 
 static inline void
 ata_queue_pio_task(struct ata_port *ap)
 {
-        queue_work(ata_wq, &ap->pio_task);
+        if (!(ap->flags & ATA_FLAG_FLUSH_PIO_TASK))
+                queue_work(ata_wq, &ap->pio_task);
 }
 
 static inline void
 ata_queue_delayed_pio_task(struct ata_port *ap, unsigned long delay)
 {
-        queue_delayed_work(ata_wq, &ap->pio_task, delay);
+        if (!(ap->flags & ATA_FLAG_FLUSH_PIO_TASK))
+                queue_delayed_work(ata_wq, &ap->pio_task, delay);
+}
+
+/**
+ *      ata_flush_pio_tasks - Flush pio_task and packet_task
+ *      @ap: the target ata_port
+ *
+ *      After this function completes, pio_task and packet_task are
+ *      guranteed not to be running or scheduled.
+ *
+ *      LOCKING:
+ *      Kernel thread context (may sleep)
+ */
+
+static void ata_flush_pio_tasks(struct ata_port *ap)
+{
+        int tmp = 0;
+        unsigned long flags;
+
+        DPRINTK("ENTER\n");
+
+        spin_lock_irqsave(&ap->host_set->lock, flags);
+        ap->flags |= ATA_FLAG_FLUSH_PIO_TASK;
+        spin_unlock_irqrestore(&ap->host_set->lock, flags);
+
+        DPRINTK("flush #1\n");
+        flush_workqueue(ata_wq);
+
+        /*
+         * At this point, if a task is running, it's guaranteed to see
+         * the FLUSH flag; thus, it will never queue pio tasks again.
+         * Cancel and flush.
+         */
+        tmp |= cancel_delayed_work(&ap->pio_task);
+        tmp |= cancel_delayed_work(&ap->packet_task);
+        if (!tmp) {
+                DPRINTK("flush #2\n");
+                flush_workqueue(ata_wq);
+        }
+
+        spin_lock_irqsave(&ap->host_set->lock, flags);
+        ap->flags &= ~ATA_FLAG_FLUSH_PIO_TASK;
+        spin_unlock_irqrestore(&ap->host_set->lock, flags);
+
+        DPRINTK("EXIT\n");
 }
 
 void ata_qc_complete_internal(struct ata_queued_cmd *qc)
@@ -3767,6 +3814,9 @@ static void ata_qc_timeout(struct ata_queued_cmd *qc)
 
         DPRINTK("ENTER\n");
 
+        ata_flush_pio_tasks(ap);
+        ap->hsm_task_state = HSM_ST_IDLE;
+
         spin_lock_irqsave(&host_set->lock, flags);
 
         switch (qc->tf.protocol) {
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 55176df403a5..f4cd1eb734a0 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -162,7 +162,8 @@ enum {
         ATA_FLAG_PIO_LBA48      = (1 << 13), /* Host DMA engine is LBA28 only */
         ATA_FLAG_IRQ_MASK       = (1 << 14), /* Mask IRQ in PIO xfers */
 
-        ATA_FLAG_IN_EH          = (1 << 15), /* EH in progress */
+        ATA_FLAG_FLUSH_PIO_TASK = (1 << 15), /* Flush PIO task */
+        ATA_FLAG_IN_EH          = (1 << 16), /* EH in progress */
 
         ATA_QCFLAG_ACTIVE       = (1 << 1), /* cmd not yet ack'd to scsi lyer */
         ATA_QCFLAG_SG           = (1 << 3), /* have s/g table? */